May 2012 Climate Summary
Drought: Most of Arizona and New Mexico continue to experience moderate drought or more severe drought conditions. The driest areas are in central and southern Arizona and eastern New Mexico.
Temperature: Warm temperatures have set in across the Southwest as a result of high pressure systems that have blocked incursions of colder and moister air.
Precipitation: Precipitation in parts of southwestern New Mexico was been 1–2 inches above average in the past 30 days, while western New Mexico and virtually all of Arizona were bone dry.
ENSO: ENSO-neutral conditions have officially returned and near-average sea surface temperatures characterize much of the equatorial Pacific Ocean. However, there is some early indication that an El Niño event is brewing.
Climate Forecasts: Warming trends in recent decades are driving forecasts for above-average temperatures in coming months. Precipitation forecasts for the monsoon, on the other hand, are not definitive, in part because the monsoon is difficult to forecast.
The Bottom Line: The historically driest time of the year for Arizona is in full swing. Precipitation in the last month totaled less than 0.5 inches for nearly the entire state, which is less than 50 percent of average. Extremely dry conditions have been a mainstay in Arizona since the end of December, and the January–March period ranks as the 13th driest on record in the state; New Mexico experienced the 10th driest on record. Despite the overall dry conditions in New Mexico, the last 14 days delivered much-needed rain to southern regions, which have been mired in extreme and exceptional drought for more than a year. Dry conditions usually favor warmer weather, and this held true in the last 30 days. In Arizona, temperatures were 4–6 degrees F above average in the past month, while New Mexico was slightly cooler. The warm and dry conditions helped expand and intensify drought. Extreme drought now occupies a large swath in the Four Corners region, and extreme drought remains entrenched in central Arizona. In Phoenix, for example, precipitation deficits in the last year amounted to 3.6 inches. La Niña, which helped cause the dry winter, waned to neutral conditions at the end of April. While it is currently difficult to project the evolution of the El Niño-Southern Oscillation (ENSO), there is some indication that an El Niño may emerge in coming months. This would increase chances for a wetter-than-average monsoon and winter. The fate of ENSO will become clearer in coming months and precipitation forecasts for the monsoon remain a coin flip.